Examples of suitable materials for the treatment with the apparatus of the invention include textiles, paper, leather, plastic films, wood, rubber, vulcanized fibers, emery cloth, and the like. As is well known, when producing lengths of such materials, it is often necessary to cool them in the course of various other processing operations, such as after a drying operation or a heat-setting operation, for example, so as to permit continuous further processing and to ensure that the material is of high quality.
For example, it is customary to dry or heat-set composite fabrics containing synthetic fibers at speeds of from 100 to 150 m/minute, the lengths of fabric emerging from the heating chamber at temperatures of between 75.degree. C. and 110.degree. C. at these speeds. If the lengths of material were to be folded and stored at such temperatures, the intrinsic weight of the stack could produce creases and kinks which would impair the quality of the material if it was piled unsuitably. However, such creasing can usually be avoided if the lengths of material are cooled down at least to room temperature, before being folded. Apart from this, the quality of the lengths of material can be improved by cooling if, during such heat-treatment operations, the length of material are kept taut widthwise (in the direction of their width) by means of spiked chains, clamps, or the like, so as to maintain dimensional stability; this dimensional stability can be much better maintained after a heat treatment, if the lengths of material are cooled immediately after the heat-treatment, possibly also while the width of the material is controlled.
Hitherto, in most cases, the lengths of material have been cooled by blowing fresh air over them. In addition, particularly when permeable materials are involved, arrangements have been used in which fresh air is drawn through the length of material by means of a vacuum with the aid of suction nozzle heads past which the length of material is led, or with the aid of perforated drums over which the length of material is passed. However, with these cooling systems, large quantities of air have to be pumped to obtain a satisfactory cooling effect given the short cooling time available with the high speeds used during the processing operations. This leads to high energy costs which are quite unjustifiable economically in many cases. Consequently, use has already been made of cooling systems in which the air is cooled in heat exchangers, for example, by means of cooling water, and only then brought into contact with the length of material. But, even with such cooling systems, substantial amounts of energy often have to be used in order to obtain a cooling speed corresponding to the speed of the individual processing operations.